The mechanisms by which various oral bacteria regulate the flow of substrate carbon within and between diverse metabolic pathways continue to be under investigation. Certain enzymes which function in constitutive pathways leading to lactic acid are being studied as possible control sites in cariogenic as well as noncariogenic streptococci. These include NAD- and NADP-linked glyceraldehyde-3-phosphate dehydrogenases, phosphofructokinase, and fructose-1,6-diphosphatase. The enzymes have been purified to various degrees and the means by which their catalytic function is modulated by interaction with specific low molecular weight ligands are being analyzed. Factors involved in regulating the synthesis of extracellular glucosyltransferases in S. salivarius and strains of S. mutans are also under investigation. BIBLIOGRAPHIC REFERENCES: Wittenberger, C.L.: Effects of fluoride on enzymatic regulation of bacterial carbohydrate metabolism. Discussion. Caries Res. 11 (suppl. 1) 287-291, 1977. Wittenberger, C.L., Beaman, A.J., Lee, L.N., McCabe, R.M. and Donkersloot, J.A.: Possible role of Streptococcus salivarius glucosyltransferase in adherence of Veillonella to smooth surfaces. In Schlessinger, D. (Ed.) Microbiology 1977, pp. 417-421.